JP2001210263A - Scanning electron microscope, dynamic focus control method thereof, and method of grasping surface and cross-sectional shape of semiconductor device - Google Patents

Abstract

(57) [Summary] In a scanning electron microscope having a dynamic focus function, a bird's-eye view observation for simultaneously observing a sample having two or more inclination angles, in particular, a surface and a cross section of a device fractured cross section or a FIB processed specimen. And to obtain an image focused on the entire field of view. A change position of a tilt angle of a sample is specified from a signal waveform after focusing. From the change position of the angle, the focus current value, the tilt angle information from the Tilt angle reading unit 17 and the observation magnification information from the magnification reading unit 18, the focus change for each scanning line corresponding to the tilt angle before and after the change position Calculate the amount ΔI, and in accordance with the scanning in the Y direction,
It is characterized in that the dynamic focus control unit 19 sequentially superimposes the current on the focus current of the objective lens power supply 20, and it is possible to prevent out-of-focus in bird's-eye view observation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning electron microscope which has a dynamic focus function and a sample tilting function and forms an image by a signal generated from the surface of a sample, and relates to observation of a tilted sample, and particularly to observation of a semiconductor device. The present invention relates to simultaneous observation of a fracture surface and a surface and a cross section of a sample subjected to FIB processing. Here, FIB processing means Focused Ion Be
This is a processing method in which an arbitrary cross section can be created at an arbitrary place by irradiating a sample with a Ga ion beam in the sense of processing by am.

[0002]

2. Description of the Related Art In general, a scanning electron microscope is known to have a large depth of focus. However, in high-resolution observation, the opening angle of an electron beam at the time of irradiating a sample is increased and the spot diameter of the electron beam is reduced. There is a need. At this time, the depth of focus is inversely proportional (shallow) to the opening angle.

[0003] Therefore, when performing high-resolution observation in a state where a sample is tilted, dynamic focus is used to eliminate blurring of focus due to a difference in height of the sample.

[0004] In addition, even when observing the surface of a single-inclined sample, when using dynamic focus,
The amount of change in focus is manually performed while looking at the screen, and the operation is complicated and requires some skill.

As a measurement method for a sample having a spread in the Z direction, for example, as shown in Japanese Patent Application Laid-Open No. 5-299048, the focus is moved back and forth to extract a focused part and its Z-axis information. There is a method of generating and displaying a bird's eye view by adding them together.

[0006]

In the actual operation of the dynamic focus, the adjustment of the amplitude of the pulse signal is performed as follows.
After focusing on the center of the screen while observing the scanning electron microscope image, a complicated operation is required to manually adjust the amount of change so that the upper and lower parts of the screen are simultaneously focused.

With the spread of focused ion beam processing equipment,
The need for observing the processed surface is increasing. In particular, in box processing, it is necessary to tilt the sample for the observation due to physical limitations, and simultaneous observation of the surface and cross section is performed to correspond to the surface structure. Here, the box processing is a processing method in which a hole is formed in a box shape from the surface of the sample in order to observe a cross section of an arbitrary portion of the sample (for example, a failed portion of the device).

In evaluating thin films in semiconductors and display devices, the surface shape, the cross-sectional structure corresponding to the shape, and the process of forming a film from the cross-sectional direction are important factors that determine the characteristics of the thin film. Simultaneous observation of the cross section is essential.

However, in the conventional dynamic focus, in the bird's-eye view observation in which the cross section and the surface of the sample are observed together, such as a fractured surface of a FIB processed sample or a semiconductor device, the inclination angle of the observation surface changes in the frame. Therefore, if the camera is adjusted to one inclination, the focus is not adjusted to the opposite side. For this reason, focus is placed on only the inclination of either the sample surface or cross section, or focus is placed on only a very small part near the transition between the surface and cross section without using dynamic focus, and observation is currently performed. is there.

However, as mentioned above, simultaneous evaluation of the surface and cross-section of thin films on the order of microns or less is indispensable in the development of elemental technologies for semiconductors and display devices, and it is desired to establish an observation method that focuses on the entire bird's-eye view. It had been.

In the case of specializing a FIB processed sample or a sample having a relatively large change in the Z-axis direction, such as simultaneous observation of the surface and cross section of a thin film, the method described in Japanese Patent Application Laid-Open No. 5-299048 described above requires a required number of images. Because of the increased amount of time required for processing, measurement at high throughput cannot be easily performed.

An object of the present invention is to automatically and simply focus on the entire field of view when there are at least two directions of sample inclination such as a FIB processed sample or a split cross section sample of a semiconductor device, especially in simultaneous observation of a surface and a cross section. An object of the present invention is to provide a scanning electron microscope which can be adjusted to the above, a dynamic focus control method thereof, and a method of grasping the surface and cross-sectional shape of a semiconductor device.

[0013]

According to the present invention, there is provided an electron gun for generating an electron beam, means for converging and irradiating an electron beam, and means for scanning an electron beam on a sample. Deflection means, a detector for detecting a signal generated from the sample surface by electron beam irradiation, means for displaying the detected signal, means for tilting the sample, and a scanning electron microscope having a dynamic focus function, The objective is to set the amount of change in the exciting current of the objective lens based on the observation conditions and observe. Thereby, in a sample having at least two or more inclinations, automatically and simply, particularly for a sample in which the angle between the inclinations of two observation surfaces such as a FIB processed surface or a split surface of a semiconductor device is 90 degrees, An object is to obtain an image in which the entire field of view is in focus.

Here, the "observation conditions" are observation conditions for obtaining a final image, and include focus current value information, tilt angle information, magnification information, and image information.

The present invention specifically provides the following apparatus and method.

According to the present invention, an electron gun for generating an electron beam, an irradiation unit for converging and irradiating the electron beam, a deflecting unit for scanning the electron beam on the sample, and an electron beam generated from the sample surface by the irradiation of the electron beam. In a scanning electron microscope equipped with a detector that detects a signal and a dynamic focus control unit that operates dynamic focus, a change position of the tilt of the sample is obtained from focus current information, and the focus change according to the tilt before and after the change position. The present invention provides a scanning electron microscope for calculating an amount and setting a change amount of an objective lens excitation current based on the focus change amount.

The present invention further comprises a display unit for displaying the detected signal on the screen, obtaining a top peak from a change in the signal waveform by the focus search, calculating the peak position, and calculating the peak position from the center of the display screen and the peak position. A scanning electron microscope for determining the position of a top peak on a display screen.

In the present invention, the change amount of the exciting current of the objective lens is read from the stage control unit or the tilt angle information read from the input device to the sample tilt angle reading unit, and read from the magnification control unit or the input device to the magnification reading unit. The present invention provides a scanning electron microscope set based on magnification information obtained and image information stored in an image memory.

The present invention further provides a current focus current by successively adding or subtracting a focus current change amount from the focus current at each scanning return time in the Y-direction scanning, and from the change position of the sample inclination to the current focus current. Provided is a scanning electron microscope in which a current focus current is obtained by sequentially subtracting or adding a focus current change amount, and a one-line objective lens excitation current is set.

According to the present invention, there is provided an electron gun for generating an electron beam, an irradiation unit for converging and irradiating the electron beam, a deflecting unit for scanning the electron beam on the sample, and an electron beam generated from the sample surface by the irradiation of the electron beam. In a scanning electron microscope equipped with a detector that detects a signal and a dynamic focus control unit that operates dynamic focus, a change position of the tilt of the sample is obtained from focus current information, and the focus change according to the tilt before and after the change position. The objective lens exciting current is set according to the amount of focus change, the objective lens exciting current set at a plurality of locations in one frame is read and stored, and the reference value of the objective lens exciting current in one frame and A scanning electron microscope for setting a change amount is provided.

According to the present invention, an electron gun for generating an electron beam, an irradiation unit for converging and irradiating the electron beam, a deflecting unit for scanning the electron beam on the sample, and an electron beam generated from the sample surface by the irradiation of the electron beam. In a dynamic focus control method for a scanning electron microscope including a detector for detecting a signal and a dynamic focus control unit for operating a dynamic focus, in a sample in which the oblique direction of an observation surface changes by 90 °, the focus current information Provided is a dynamic focus control method for a scanning electron microscope that calculates a change position of an inclination and calculates a focus change amount caused by a 90 ° change in the observation plane direction.

According to the present invention, there is provided an electron gun for generating an electron beam, an irradiation unit for converging and irradiating the electron beam, a deflecting unit for scanning the electron beam on the sample, and an electron beam generated from the sample surface by the irradiation of the electron beam. In a dynamic focus control method of a scanning electron microscope including a detector for detecting a signal and a dynamic focus control unit for operating a dynamic focus, a sample is tilted at an arbitrary angle, and a change position of the tilt of the sample is obtained from focus current information. A dynamic focus control method for a scanning electron microscope which calculates a focus change amount due to a tilt before and after a change position from respective focus currents at a tilt change position and a scan end position.

According to the present invention, in a method for grasping the surface and cross-sectional shape of a semiconductor device by a scanning electron microscope, the semiconductor device is inclined at an arbitrary angle, a change position of the sample inclination is obtained from focus current information, and the inclination before and after the change position is determined. The present invention provides a method for grasping the surface and cross-sectional shape of a semiconductor device, in which the amount of change in focus accompanying the calculation is calculated, the exciting lens current is controlled, and the surface and cross-section of the display screen in the same field of view are obtained as one image.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIGS. 2 and 3 are partially detailed views of FIG. In these figures, an electron beam 4 obtained by an electron gun 1, an extraction electrode 2 and an acceleration electrode 3 is converged on a surface of a sample 7 by a condenser lens 5 and an objective lens 6. At this time, the magnification information is transmitted from the magnification control unit 10 to the X-direction scan control unit 11 and Y
The direction is transmitted to the direction scanning control unit 12 and the scanning control unit 1
From 1 and 12, the scanning pulse signal corresponding to the magnification is X
The electron beam 4 scans the surface of the sample 7 by being input to the directional scanning coil 8 and the Y-directional scanning coil 9, respectively. At this time, the secondary electrons 22 generated from the sample surface are detected by the detector 23 to become a signal, which is displayed as a scanning electron microscope image, and at the same time, the signal is stored in the image memory 27 as an image signal. The sample stage 13 includes a sample tilt operation device (not shown), and performs sample tilt and sample movement under the control of the stage controller 14.

The current value information read from the objective lens 6 by the focus current reading unit 15 and the stage control unit 1
4 or the tilt angle information read by the tilt angle reading unit 17 from the input device 16, the magnification information read by the magnification reading unit 18 from the magnification control unit 10 or the input device 16, and stored in the image memory 27. Based on the image information (memory address), as shown in FIG. 2, the dynamic focus control unit 19 adjusts the inclination (end surface) position Pn (described later) in the Y-direction scanning and the inclination before and after the end surface position. Calculate the focus change amount Δf (described later),
It is possible to focus on the entire surface of the sample by superimposing it on the objective lens power supply 20. At this time, the responsiveness of a focus change can be improved by using a dedicated coil having a small number of turns or the electrostatic auxiliary lens 90.

Secondary electrons 22 generated from the sample surface 21
Is detected by the detector 23. The detected electrons are used as signals on the display screen of the cathode ray tube 24 to synchronize the X direction scanning coil 8 and the Y direction scanning coil 9 with each other.
Scanning is performed by the directional scanning coil 25 and the cathode ray tube Y-directional scanning coil 26, and displayed as a scanning electron microscope image. The image signal is stored in the image memory 27 simultaneously with the display.

At the time of electron beam scanning, a short-period X-direction scanning pulse signal 31 and a long-period Y
A direction scanning pulse signal 32 is input to each scanning coil. In the scanning time 33, the X-direction scanning pulse signal 31 changes, and the X-direction scanning is performed. At this time, Y
The direction scanning pulse signal 32 does not change, and the Y direction scanning is not performed. In the scan return time 34, the X direction returns to the original scanning position, and the Y direction scanning moves by a fixed amount. By the movement at this time, the scanning line advances one line in the Y direction. By repeating this cycle, scanning 35 for one frame is performed on the sample surface as shown in FIG.

FIG. 5 shows a flow as an example of the embodiment of the present invention. First, a target visual field is displayed on a screen (501). At this time, the axis of inclination is adjusted in the X direction by mechanical rotation or raster rotation. Record Mag. (Observation magnification) and Tilt (sample tilt angle) (502)
Then, the value is displayed to the operator (503). At this time, in the case of No, the magnification and the inclination angle are input from a keyboard or the like (504), the process returns to Step 502, and the process is repeated until the result of Step 503 becomes Yes. If Yes, auto focus (505) is performed, and the value of the focus current I at that time is changed to the focus current I (St
d) (506). Step 506
This is due to the fact that in the bird's eye view observation, the auto focus is focused on the end face position. Raster rotation (507) and Focus Search (508) are performed in the clockwise direction with the current viewing condition plus 90 degrees, and Top Pe of the image signal is performed.
The ak position is detected (509), and the end face position Pn is calculated (510).

FIG. 7 shows a conceptual diagram of the operation in steps 507 to 510. In step 507, since Focus Search in step 508 is performed in the X direction,
This is a step for adjusting the end face position Pn with respect to the direction in the X direction. In steps 508 to 509, when the end face position Pn is in focus, the top peak (Top Peak) 72 of the signal waveform 71 obtained by the focus search is the position. Step 510
Is a step of calculating an end face position 75 (described later) from a distance 74 between two points on the display screen between the top peak 72 and the center 73 of the display screen. Top peak 7 at this time
2 and the position of the center 73 of the display screen are stored in the image memory unit 27.
Pixel address. Further, the distance 74 between the two points is obtained by converting the value of the X value of the pixel address between the two points into a distance on the display screen.

As shown in FIG. 6, Mag., Tilt (θ), P
From the value of n, the Y-direction scanning start position P1 to the end surface position Pn
(F1, Pn) and the focus change Δf (Pn, Pmax) from the end face position Pn to the Y-direction scanning end position Pmax (described later) (511).

Δf (P1, Pn) obtained from the above steps,
From the values of Δf (Pn, Pmax) and I (Std), a focus current I (P1) at the Y-direction scanning start position P1 and a focus current I (Pmax) at the Y-direction scanning end position Pmax are calculated. This will be described later (512).

I (P1) and I (Pma
x), the focus current change amount Δ per scanning line in the section from the Y-direction scanning start position P1 to the end surface position Pn.
I (P1, Pn) and Y-direction scanning end position Pm from end face position Pn
The focus current change amount ΔI (Pn, Pmax) per scanning line in the section up to ax is calculated (described later) (513).

The following steps correspond to the above steps 511 to 511
513, ΔI (P1, Pn), ΔI (Pn, Pmax),
This is a step of sequentially changing the focus amount using I (P1) and I (Pmax). The focus current I is set to I (P1) (514). One line is scanned in the Y direction (515).
At this time, the scanning in the Y direction advances by a scanning time 33. Until the number of scanning lines ln in the Y direction becomes ln (Pn) (described later), the focus current change amount ΔI (P1, Pn) is sequentially added to the focus current I every time the scanning return time 34 is reached (516 to 51).
7).

When ln becomes ln (Pn), the process proceeds to the next step, and in the section of the scan return time 34, the focus current change amount ΔI (Pn, Pmax) is sequentially subtracted from the current focus current I (518). , Then Y as in step 515
One line is scanned in the Y direction, and the number of scanning lines ln in the Y direction is ln (P
max) (to be described later), the focus current change amount ΔI (P
n, Pmax) are sequentially subtracted (518 to 520). When the determination at Step 520 becomes Yes, the scanning for one frame is completed, and the final focus current I becomes I (Pmax).

By the above steps 514 to 520, the focus current I changes along the sample inclination, and a bird's-eye view image in which the whole is focused can be obtained.

The method of calculating the end face position Pn in the above-described step 510 will be described below with reference to FIG. The amount of scanning movement and the number of scanning lines on the sample from the scanning start position P1 in the Y direction to the end surface position Pn are represented by y (Pn) 76 and l, respectively.
n (Pn), and the scanning movement amount and the number of scanning lines on the sample from the Y-direction scanning start position P1 to the Y-direction scanning end position Pmax are y (Pmax) 77 and ln (Pmax), respectively. Here, y (Pmax) and ln (Pmax) are the same as the total scanning movement amount and the total number of scanning lines in the Y direction on the sample, respectively. Therefore, when the display width in the Y direction on the final display screen is Ly and the magnification is M, the total scanning movement amount in the Y direction is represented by y (Pmax) = Ly / M- (Equation 1). Accordingly, the amount of movement y (1) in the Y direction per scanning line on the sample is expressed by the following equation.

Y (1) = y (Pmax) / ln (Pmax) − (Equation 2) The number of scanning lines in the Y direction up to the center of the display screen, ln (center)
Is represented by the following equation.

Ln (center) = ln (Pmax) / 2− (Equation 3) Further, the number of pixels in the X direction from the center of the screen to the Top Peak obtained from the pixel address of the image memory unit 27 is expressed as Pixel (XT−
C), assuming that the total number of pixels in the Y direction is Pixel (Y), the distance LT-C between two points on the display screen is: LT-C = Pixel (XT-C) · Ly / Pixel (Y) − ( Equation 4) The above equation indicates that the number of pixels (XT-C) in the X direction is 90
Since the value is a value after the raster rotation, the number of pixels is substantially the same as the number of pixels in the Y direction before the raster rotation. Further, the number of scanning lines ln (LT-C) is as follows: ln (LT-C) = ln (Pmax) .LT-C / Ly- (Equation 5). Thus, the number of scanning lines ln (P
n) is given by: ln (Pn) = ln (center) ± ln (LT-C) − (Equation 6) = ln (Pmax) · (0.5 ± LT-C / Ly) − (Equation 7) Therefore, according to (Equation 1), (Equation 2) and (Equation 7), the movement amount y (Pn) 76 to the end face position Pn is represented by y (Pn) = ln (Pn) · y (Pmax) / ln (Pmax) − (Equation 8) = (0.5 Ly ± LT−C) / M− (Equation 9) The number of scanning lines ln (Pn) at the end face position Pn is obtained from (Equation 7), and the moving amount y (Pn) 76 is obtained from (Equation 9). ± in (Equation 6), (Equation 7) and (Equation 9) means addition when the position of the Top Peak 72 is on the left side of the screen center 73, and conversely when it is on the right side, as in this example. It becomes a subtraction.

FIG. 8 is a schematic diagram of the operation in steps 511 to 513, showing that Δf (P1, Pn), Δf (Pn, Pmax), I (P1), I
Formulas for calculating the values of (Pmax), ΔI (P1, Pn) and ΔI (Pn, Pmax) are shown below. As shown in FIG. 8, when the electron beam 4 is scanned on the sample (cross section) 81, the required change amount Δf (P1, P1) of the focus from the Y direction scanning start position P1 to the end surface position Pn.
n) 82 and the Y-direction scanning end position Pmax from the end face position Pn
The required change amount Δf (Pn, Pmax) 83 of the focus up to
From the above y (Pn) and y (Pmax), it is expressed by the following equation.

Δf (P1, Pn) = y (Pn) · tan θ− (Equation 10) Δf (Pn, Pmax) = (y (Pmax) −y (Pn) · tan (90−θ) − (Equation 11) Here, in FIG. 8, y (Pn) is set to 84 and (y (Pmax) −
y (Pn)) corresponds to 85. Accordingly, the working distance at the end face position Pn obtained from I (Std) is represented by d
(Pn), the focus current amount I (P1) required at the Y direction scan start position P1 and the focus current amount I (Pmax) required at the scan end position Pmax are I (P1) = k · (d (Pn) + Δf (P1, Pn)) − (Expression 12) I (Pmax) = k · (d (Pn) + Δf (Pn, Pmax)) − (Expression 13) K in the figure is a constant determined by the acceleration voltage, the number of coil turns of the lens, the shape of the lens, and the like.

From this, the focus current change ΔI (P1, Pn) per Y-direction scanning line in the section from the Y-direction scanning start position P1 to the end surface position Pn, and the focus current change ΔI (P1, Pn) from the end surface position Pn to the scanning end position Pmax The focus current change amount ΔI (Pn, Pmax) per Y-direction scanning line in the section is ΔI (P1, Pn) = I (P1) / ln (Pn) − (Equation 14) ΔI (Pn, Pmax) = I (Pmax) / (ln (Pmax) −ln (Pn)) − (Equation 15)

In the above embodiment, step 505
Although the auto focus is used, manual focusing may be performed.

In the present embodiment, the angle of the observation surface of the sample changes by 90 degrees. This is because the FIB processed surface is processed by irradiating the sample surface with an ion beam in a direction perpendicular to the sample surface, and the split surface of the semiconductor device is cleaved by the crystal orientation of the Si substrate. Is approximately 90 degrees.

The angle between the two observation surfaces of the sample is
If the angle is not 90 degrees and is not known, in addition to the focus current I (Std) at the end face position Pn, the focus is adjusted to the scan end position Pmax, and the focus current I (Pmax) at that time is stored, and the Y-direction scan line is stored therefrom. The focus current change amount ΔI (Pn, Pmax) per one is calculated, and the focus current I
An image can be obtained by successively subtracting (= I (Std)).

If the sample cannot be mounted horizontally on the sample table due to the shape of the sample, the sample tilt angle becomes an unknown value.
Focusing is performed on each of the Y-direction scanning start position P1, the end surface position Pn, and the scanning end position Pmax, and the respective focus currents are stored as I (P1), I (Std), and I (Pmax). At this time, the focus current change amounts ΔI (P1, Pn) and ΔI (Pn, Pmax) per Y-direction scanning line are ΔI (P1, Pn) = | I (P1) −I (Std) | / ln ( Pn) − (Equation 16) ΔI (Pn, Pmax) = | I (Std) −I (Pmax) | / ln (Pmax) − (Equation 17) Therefore, from the Y-direction scanning start position P1 to the end surface position Pn, the focus current I (= I (P1)) is set to ΔI (P1, P
n) is sequentially added for each scanning line in the Y direction,
From the end face position Pn to the scan end position Pmax, an image can be obtained by sequentially subtracting ΔI (Pn, Pmax) from the focus current I (= I (Std)) for each Y-direction scanning line.

FIG. 9 is a schematic diagram showing the dynamic focus operation. Normally, as shown in FIG. 4A, when the sample is tilted, since the angle of the sample surface 41 does not match the focus surface 42 of the electron beam 4, the sample surface 43 corresponding to the upper part of the display screen and the lower part of the display screen are displayed. Equivalent sample surface 44
The image becomes out of focus. At this time, the pulse signal 50 input to the objective lens power supply 20 is as shown in the figure. At this time, a focus current waveform (without inclination) 45 input from the objective lens power supply 20 to the objective lens 6
Is a constant value as shown in the figure.

Therefore, as shown in FIG. 9B, the dynamic focus is operated, and the pulse signal 46 adjusted in the Y-direction scanning according to the focus change amount as described above is passed through the objective lens power supply 20 to focus the objective lens 6. By superimposing the current on the current, the focus position changes in accordance with the scanning in the Y direction, the sample surface 41 and the focus surface 42 overlap, and an image in which the entire surface is focused can be obtained. At this time, the focus current waveform (inclined) 47 input from the objective lens power supply 20 to the objective lens 6 is a pulse signal as shown in the figure.

FIG. 9C shows the inclination on the opposite side.
As described above, this can be handled by superimposing the pulse signal 48 adjusted by inverting the polarity of the Y-direction scanning on the focus current. Focus current waveform at this time (with reverse slope) 4
9 is a pulse signal as shown in the figure.

An electron gun for generating an electron beam, means for converging and irradiating the electron beam, deflecting means for scanning the electron beam on the sample, and detection for detecting a signal generated from the sample surface by the electron beam irradiation Device, a means for displaying the detected signal, a means for tilting the sample, and a dynamic focus function, by separately reading and storing the objective lens excitation current at a plurality of points in one frame, A reference value and a change amount of the objective lens exciting current can be set. Further, the amount of change in the objective lens exciting current can be changed in one frame.

The amount of change in the objective lens exciting current can be changed on the assumption that the tilt angle of the sample has changed, for example, by 90 degrees.

When observing both the cross section and the surface at the same time, the observation can be performed with the entire field of view in focus.

When the present invention is applied to grasp the line pattern of a resist 103 with an oxide film 102 on a substrate 101 such as a semiconductor inclined at θ as shown in FIG. 10 (FIG. 9).
(A)) Since the concavities and convexities are opposite to those of the above embodiment, FIG.
In (b), Expression 10 and Expression 11 are respectively expressed by Δf (P1, Pn) = y (Pn) · tan (90−θ) − (Expression 18) Δf (Pn, Pmax) = (y (Pmax) −y (Pn)) · tan θ − (Equation 19), and an image is acquired by adding the subtraction in step 517 to the subtraction and the subtraction in step 518 to the addition to obtain the roughness of the resist side portion and the fine shape of the oxide film surface. Can grasp.

Further, a customer usage pattern is that, for example, when a surface and a cross section in the same field of view are photographed as a set of two images corresponding to respective inclination directions for thin film evaluation,
According to the present invention, it is sufficient to obtain one image. This indicates that the photographing time after determining the visual field is reduced by half, and the efficiency is effectively improved particularly when a large number of samples are measured in a wide range on a routine work.

[0055]

According to the present invention, when observing a sample having two or more inclination angles, it is possible to solve the problem that an image in which the entire field of view is in focus cannot be obtained. A scanning electron microscope capable of easily obtaining a bird's-eye view image in which both the sample surface and the cross section are simultaneously focused can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a scanning electron microscope according to the present invention.

FIG. 2 is a block diagram showing a part of FIG. 1 in detail.

FIG. 3 is a block diagram showing a part of FIG. 1 in detail.

FIG. 4 is a diagram showing a scanning pulse signal waveform in a scanning electron microscope.

FIG. 5 is a diagram showing one operation flowchart of the embodiment of FIG. 1;

FIG. 6 is a diagram showing an operation flowchart of the embodiment of FIG. 1 subsequent to the operation flowchart of FIG. 5;

7 is a step 507 in the operation flowchart of FIG. 5;
509 is a schematic diagram showing the operation.

FIG. 8 is a step 511 in the operation flowchart of FIG. 6;
It is a schematic diagram showing operation of -513.

FIG. 9 is a schematic diagram of an operation of dynamic focus.

FIG. 10 is a schematic diagram showing the operation of another embodiment according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electron gun, 2 ... Extraction electrode, 3 ... Acceleration electrode, 4 ... Electron beam, 5 ... Condenser lens, 6 ... Objective lens, 7 ...
Sample, 8: X-direction scanning coil, 9: Y-direction scanning coil,
10: magnification control unit, 11: X-direction scanning control unit, 12: Y
Directional scanning control unit, 13: sample stage, 14: stage control unit, 15: focus current reading unit, 16: input device, 17: tilt angle reading unit, 18: magnification reading unit, 1
Reference numeral 9: dynamic focus control unit, 20: objective lens power supply, 21: sample surface, 22: secondary electron, 23: detector, 24: cathode ray tube, 25: cathode ray tube X direction scanning coil, 26: cathode ray tube Y direction scanning Coil, 27: Image memory unit, 31: X direction scanning pulse signal, 32: Y direction scanning pulse signal, 33: scanning time, 34: scanning return time,
35: scanning for one frame, 41: sample surface, 42: focus surface, 43: sample surface corresponding to the upper part of the display screen, 4
4: Sample surface corresponding to the lower part of the display screen, 45: Focus current waveform (without slope), 46: Pulse signal with adjusted amplitude, 47: Focus current waveform (with slope), 48: Inverted polarity and adjusted amplitude Pulse signal, 49: focus current waveform (with reverse slope), 50: pulse signal, 71 ...
Signal waveform, 72: Top Peak, 73: Center of display screen, 74: Distance between two points on the display screen, 75
... End face position, 76 ... Scanning movement amount y (Pn) on the sample,
77: scanning movement amount y (Pmax) on the sample, 81: sample (cross section), 82: required change amount of focus Δf (P1, Pn), 8
3: required change amount of focus Δf (Pn, Pmax), 84: y
(Pn), 85 ... (y (Pmax) -y (Pn)), 90 ... electrostatic auxiliary lens, 101 ... substrate, 102 ... oxide film, 103 ... resist.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshine Nakagawa 1040 Ma, Ichiki, Hitachinaka City, Ibaraki Prefecture Inside Hitachi Science Systems Co., Ltd. (72) Atsushi Muto 1040 Ma, Ichimo, Hitachinaka City, Ibaraki Prefecture Hitachi, Ltd. F-term in Science Systems (reference) 5C033 MM03 MM05

Claims (8)

[Claims] An electron gun for generating an electron beam, an irradiation unit for converging and irradiating the electron beam, a deflecting unit for scanning the electron beam on a sample, and a signal generated from the sample surface by the electron beam irradiation. In a scanning electron microscope equipped with a detector for detecting and a dynamic focus control unit for operating dynamic focus, a change position of a sample tilt is obtained from focus current information,
A scanning electron microscope wherein a focus change amount is calculated in accordance with an inclination before and after a change position, and a change amount of an objective lens exciting current is set based on the focus change amount. 2. A display unit according to claim 1, further comprising a display unit for displaying a detected signal on a screen, calculating a top peak from a change in a signal waveform by a focus search, calculating the peak position, and calculating a center and a peak position of the display screen. A scanning electron microscope wherein the position of the top peak is determined on a display screen from the following. 3. The apparatus according to claim 1, wherein the amount of change in the objective lens exciting current is the tilt angle information read into the sample tilt angle reading unit from the stage control unit or the input device, the magnification control unit or the magnification reading unit from the input device. A scanning electron microscope which is set based on magnification information read into the image memory and image information stored in an image memory. 4. The focus current according to claim 1, wherein a change amount of the focus current is sequentially added to or subtracted from the focus current at every scanning return time of the Y-direction scanning to obtain a current focus current. A scanning electron microscope wherein a current focus current is obtained by sequentially subtracting or adding a focus current change amount to a current, and a one-line objective lens excitation current is set. 5. An electron gun for generating an electron beam, an irradiation unit for converging and irradiating the electron beam, a deflection unit for scanning the electron beam on the sample, and a signal generated from the sample surface by the electron beam irradiation. In a scanning electron microscope equipped with a detector for detecting and a dynamic focus control unit for operating dynamic focus, a change position of a sample tilt is obtained from focus current information,
Calculate a focus change amount corresponding to the inclination before and after the change position, set an objective lens excitation current based on the focus change amount, read and store the set objective lens excitation currents at a plurality of locations in one frame, and A scanning electron microscope wherein a reference value and a change amount of an objective lens exciting current in a frame are set. 6. An electron gun for generating an electron beam, an irradiation unit for converging and irradiating the electron beam, a deflecting unit for scanning the electron beam on the sample, and a signal generated from the sample surface by the electron beam irradiation. In a dynamic focus control method of a scanning electron microscope including a detector for detecting and a dynamic focus control unit for operating dynamic focus, in a sample in which a tilt direction of an observation surface changes by 90 °, a tilt of the sample is determined from focus current information. A dynamic focus control method for a scanning electron microscope, wherein a change position is obtained, and a focus change amount accompanying a 90 ° change in the observation plane direction is calculated. 7. An electron gun for generating an electron beam, an irradiation unit for converging and irradiating the electron beam, a deflecting unit for scanning the electron beam on the sample, and a signal generated from the sample surface by the electron beam irradiation. In a dynamic focus control method of a scanning electron microscope including a detector for detecting and a dynamic focus control unit for operating dynamic focus, a sample is tilted at an arbitrary angle, and a change position of the tilt of the sample is obtained from focus current information and changed. A dynamic focus control method for a scanning electron microscope, wherein a focus change amount accompanying a tilt before and after a position is calculated from respective focus currents at a tilt change position and a scan end position. 8. A method for grasping the surface and cross-sectional shape of a semiconductor device by using a scanning electron microscope, wherein the semiconductor device is inclined at an arbitrary angle, a change position of the sample inclination is obtained from focus current information, and the inclination position before and after the change position is determined. A method for grasping a surface and a cross-sectional shape of a semiconductor device, comprising calculating a focus change amount, controlling an exciting lens current, and acquiring a surface and a cross-section in the same field of view of a display screen into one image.